Creating a render target -> texture

[Chessnut]

I need a script that can create a render target and make it into a texture to draw.

I know it'd look something like this:
[lua]
local new = GetRenderTarget("newRender", 256, 256);

render.SetRenderTarget(new)
--Stuff for the RT.
render.SetRenderTarget(render.GetRenderTarget())

textureforRT:SetMaterialTexture("$basetexture", new);
[/lua]

But when I try I just end up crashing the game.